1. Field of the Invention
The present invention relates to thermal and sound insulation for objects, such as insulation installed within vehicles (e.g., aircraft, trains, boats, automobiles, trucks, and the like).
2. Description of Related References
Thermal insulation is widely employed in a variety of applications. While adding comfort and improved efficiency in certain common vehicle uses, like in automobiles, such insulation is critical to proper operation of other vehicles, such as maintaining a temperature gradient in high flying aircraft.
Insulation installed in many of today's vehicles must meet very stringent thermal and acoustic insulation requirements. As a result, the insulation material is often tightly packed into constricted areas and around many objects to ensure maximum insulation. Also, the insulation must perform under a wide range of environmental conditions. These demands are particularly strict in the design of aircraft which regularly undergo dramatic temperature, pressure, and humidity changes. Although not as extreme, other vehicles such as trains, automobiles and trucks, and watercraft, may also require considerable air-conditioning and acoustical insulation.
Complicating the process of insulating vehicles is the fact that their shells may contain many obstructions that insulation material must be fitted around (e.g., pipes, stringers, tubes, and structural ribs). Presently, to situate the insulation around ribs, stringers, and other similar obstructions, insulating material is either cut to size and a custom cover is formed to fit, or loose insulation is merely "stuffed" around the obstructions. In making customized covers, copious amounts of pressure sensitive tape are manually applied to the cover in order to close the seams and make a seal. Neither of these approaches is fully satisfactory. With the production of customized covers in particular, this is highly labor intensive and slow.
In addition to the space constraints, insulation must endure temperature and pressure variations. Very tightly sealed vehicles, such as jet aircraft, can experience extensive moisture build-up in the passenger cabin from breath, perspiration, steam from foods, etc. When the exterior of such vehicles is at a substantially lower temperature than the interior, the moisture vapor in the interior air tends to condense on the shell or within insulation surrounding the shell.
The build-up of moisture within insulation lining a vehicle's shell is a multi-faceted problem. First, many insulation materials commonly used today, such as fiberglass and certain foams, have a tendency to retain water once wetted. As a result, the insulation increases in its weight over time as condensation forms and remains within the; insulation. In vehicles where weight increases can result in substantial differences in fuel costs (e.g., aircraft), this build-up of moisture results in astronomical waste in fuel.
Second, the build-up and retention of water also poses a number of safety and health hazards. For example, the accumulation of water: (a) contributes to a corrosive environment on the concealed interior of the vehicle's shell and, if left unchecked, can weaken important structural parts; (b) reduces the maneuverability of the vehicle through excessive weight gain; and (c) promotes an unsanitary environment where microorganisms can grow.
Third, the presence of moisture in certain insulation will tend to distort or decay the insulation over time. This occurs dye to the increased weight of wet insulation in sidewalls which draws the insulation downward. Eventually gaps will develop which reduces both the thermal and acoustical insulative properties of the insulation. Water will also decay certain insulation materials which can further reduce their insulative properties.
Earlier insulations employed in aircraft and similar vehicles were simply loose fibers or batts packed between the shell of the vehicle and the interior walls. Among the deficiencies of this insulation system was that it tends to be hard to install and maintain, glass fibers are a health hazard during installation and removal, and the insulation tends to slide out of position.
More recently in the aircraft industry it has been recognized that the insulation should be regularly removed so that the interior of the fuselage can be inspected for corrosion and other problems. To accomplish this, a number of companies have begun wrapping insulation material with individually wrapped covers, such as a casing of MYLAR.RTM. polyester film or other impermeable membrane which resists liquid and moisture vapor penetration. While such materials are effective at preventing moisture migration through the cover, sometimes breathing holes must be added to the air impermeable water proof casings to allow air to vent out when the pressure changes. These pressure compensation holes have resulted in the inevitable ingress of moisture vapor and water build-up. Moreover, the fact that the casing material is essentially liquid and vapor impermeable means that, once the insulation becomes damp, the insulation package remains wet for a very long period of time.
In the parent application, it is disclosed that a protective water resistant, vapor permeable cover may be used as a wrap around insulation material. When installed within a vehicle, moisture vapor freely enters and leaves the insulative package, but condensate which may form within the insulative package is contained therein and does not leak out to cause problems within the vehicle. Since the cover is "breathable" to moisture vapor, condensation which may form within the insulative package is free to evaporate and dissipate when conditions permit. This is believed to be a major improvement in insulation packaging. But, it is also believed that further improvements are still possible.
For instance, existing covers have been designed to be tight fitting--matching the exact contours of the covered insulation. However, these tight fitting covers are expensive to produce and buy because a cover must be custom made for different shaped pieces of insulation material. This is a substantial cost considering that a typical large passenger jet air craft may have over 1300 different sized pieces of insulation. Custom fitted covers are a particular problem where insulation material must fit closely around unusual shaped objects, in tight spaces, or along curved surfaces. Presently there is no easy way to wrap such insulation with a cover. This has resulted in the use of loose (uncovered) insulation material (with its inherent handling problems) in tight applications or the laborious wrapping and sealing of each piece of irregularly shaped insulation. Neither of these solutions is believed satisfactory.
Accordingly, it is a primary purpose of the present invention to provide an insulation package having a cover which is easy to fit around irregular shaped insulation material.
It is another purpose of the present invention to provide an insulation package that can be readily installed or removed and maintained when positioned in tight areas or around objects to be insulated.
It is a further purpose of the present invention to provide an insulation package having a durable cover which has liquid water impermeable sections and vapor moisture permeable sections so that liquid water contained within the cover can evaporate.
These and other purposes of the present invention will become evident from review of the following specification.